In the known way, moulding devices of this type can be used to create containers, such as bottles, from thermoplastic preforms. The preforms are preheated to a glass transition temperature to make them sufficiently malleable. The preform thus heated is inserted into the moulding cavity, then a blow nozzle injects a pressurized blow-moulding fluid, generally air, into the preform so that the walls of the latter conform to the impression delimited by the moulding cavity.
When the plastic containers have to be filled with a hot liquid, a container moulded at an ambient temperature carries the risk of container shrinkage and deformation. To avoid this shrinkage phenomenon, the mould has to be heated to a determined temperature, for example between 130° C. and 180° C., during the moulding operation in order to make the plastic of which the container is made heat resistant.
Various ways of heating the mould are already known. Thus, it is known practice to heat the mould using a fluidic circuit created within the thickness of the mould. A hot heat-transfer fluid is fed into the circuit in order to heat the mould.
It is also known practice to arrange heating electrical resistances within the thickness of the mould in order to heat the mould electrically.
Certain operations require an operator to handle the mould. Such is the case for example when there is a change in format of container to be manufactured. However, the operator cannot handle the mould while it is still hot and it is not a viable option to wait for the mould to cool down passively, thus bringing the entire production line to a standstill.
In order to solve this problem, it is known practice to use mould cooling means.
Thus, when the mould is heated by a hot heat-transfer fluid circuit, it has already been proposed that the hot heat-transfer fluid be temporarily replaced with cold heat-transfer fluid. Such a method allows the mould to be cooled rapidly.
The manufacture of a mould equipped with a heat-transfer fluid circuit devoted to cooling is extremely expensive and complicated to achieve because of the presence of the heating resistances within the thickness of the mould.